aggression issues?

[jubjubrsx]

i have 2 halfblack angels(pretty big like 3"bodies) and a 3-4" green severum in my tank lately aggression has really put a hurtin on one of the angels they were fine for quite a while, but with some aggression but nothing that bad....

figuring plants might help i put alot of plastic plants in for some cover and that only seemed to make the aggression worse.

i woke up this morning to find one of my angels floating kinda sideways near the top and i noticed his bottom fin and tail were noticeably shorter....

help!? i really dont want him to die...i dont/cant put him in another tank (condo restrictons maxed out the tank size already)...

any suggestions would be nice:look:

 

[Slevin]

you can try too add some more fish. This might spread out the aggression so instead of one or two fish getting beaten up badly it will be a bunch of fish just gettin hurt a little.

 

[trankill]

I'm just a begginer, but maybe if you add more, the severum will feel threaten and less prone to be aggressive? can that be possible? I've heard of it somewhere. I'm also thinking of having a Green severum in my tank.